Reflection of incident light reduces the efficiency (photocurrent) of silicon solar cells. Without antireflection, about 40% of sunlight is lost. This anti-reflection must be effective across the entire solar spectrum and at a wide variety of incident sunlight angles. Acceptance of light from a broad range of angles aids in capturing morning, afternoon, and diffuse scattered light. These same antireflection properties are also useful in silicon-based optical detectors.
Presently, antireflection on crystal silicon photovoltaics is achieved through several different techniques, but none is completely satisfactory. Anisotropic (pyramidal) texture etching of single crystal silicon reduces reflectivity to about 5-15% on 100-oriented single-crystal silicon, but mainly for light incident at angles near 90° and not for low incident angles. This technique also consumes a lot of silicon material, making it impractical for film silicon photovoltaics. On other forms of silicon and silicon solar cells, deposited, quarter-wavelength films of ITO, SiOx, SiNx or other materials are used to reduce reflectivity, but the effect is based on interference and therefore tuned to a specific wavelength and is not necessarily effective across the entire solar spectrum. Averaged across the solar spectrum, reflection can be reduced to about 5-15%. Lower-reflection approaches that work effectively at all incident angles are still needed.
Previous black silicon etching approaches result in low reflectivity across the entire solar spectrum and a wide range of angles of incidence, but the gold evaporation step is expensive to implement and difficult to control.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.